Clinical Trial: Gabapentin for Prophylaxis Intrathecal Morphine-Induced Pruritus

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Gabapentin for Prophylaxis Intrathecal Morphine-Induced Pruritus After Orthopedics Surgery

Brief Summary:

Intrathecal morphine provides good postoperative analgesia for up to 18-24 hour after administration. Pruritus is the most common side effect of intrathecal morphine, which the incidence was reported as 20%-100%2 and 63% in Songklanagarind Hospital. Pathophysiology of opioid-induced pruritus remain unclear and more than one mechanism may be involved in the development of opioid-induced pruritus, such as, mediated central µ opioid receptors, Dopamine (D2) receptors, Serotonin (5-HT3) receptors, prostaglandin system, GABA receptors, and glycine receptors, so that why opioid-induced pruritus is difficult to manage. Many medications have been used to treat this side effect included antihistamines, 5-HT3 (serotonin) receptor antagonists, opioid antagonists, opioid agonist-antagonists, propofol, and nonsteroidal antiinflammatory drugs.

Gabapentin is an anticonvulsant, a structural analog of aminobutyric acid, and currently approved by the Food and Drug Administration for the treatment of partial seizures and postherpetic neuralgia. Many studies have shown gabapentin to be effective in the case of brachioradial pruritus, itch of neuropathic in origin, uremic pruritus, multiple sclerosis-induced pruritus,cholestatic pruritus, itch produced by burn, and pruritus of unknown origin. However, there is only one small study in Taiwan shown the effectiveness of gabapentin 1200 mg in prevention of intrathecal morphine-induced pruritus in orthopedic surgery, which could reduce incidence of pruritus from 77.5% to 47.5% (38.7% reduction). Because gabapentin has several side effects especially in high dose such as drowsiness, dry mouth, headache, unsteadiness, reduced co-ordination or slowed reaction, constipation, diarrhea, peripheral edema, dizziness, confusion, loss of concentration, weight gain, and nausea, vomiting, so in our study we decided to reduce the dose of gabapentin. There

Detailed Summary: The study was approved by the ethic committee of Songklanagarind Hospital in Songkhla, Thailand, and was designed as a randomized, double-blind, placebo-controlled trial. All patients gave their informed consent after receiving written information of the study. Orthopedic patients were invited to participated between September 2009 and August 2010. Patients were considered eligible if they were aged between 15-70 yr, ASA physical status I-III, and were scheduled for lower limb surgery under spinal anesthesia. Patients were excluded if they presented of any following reasons: contraindication for spinal anesthesia, known allergy history to gabapentin, complaint of pruritus before surgery, morbid obesity (BMI > 35), coexisting skin disorder, and any systemic disease associated with pruritus. Patients who had history of seizure attacks, mental illness, chronic headache, or neuropathic pain and were concomitantly using of anticonvulsants, antidepressants, antipsychotics, or antihistamine were also excluded. Patients were randomized into the treatment and the placebo groups according to a computer-generated randomization list and patients were allocated consecutively. The blinding was maintained by keeping the treatment code with one of the investigators, separating them from the investigator performing the assessments. Patients in the gabapentin group received two capsules of gabapentin 300 mg (Neurontin®, Pfizer) at 2 h before operation. The patients in the placebo group received equal numbers of identical looking placebo, according to the same schedule. In order to prepare the identical looking medications, for gabapentin group we coated gabapentin capsules by other capsules and for placebo group we filled the identical looking capsules with flour. All patients did not receive any other sedative agents beside the study drugs. After standard monitoring (electrocardiogram, noninvasive arterial blood pressure, and pulse oximetry) was set-up in the operating room,
Sponsor: Prince of Songkla University

Current Primary Outcome: incidence of pruritus postoperatively [ Time Frame: 0-24 h ]

Original Primary Outcome: Same as current

Current Secondary Outcome: onset time and severity of pruritus [ Time Frame: 0-24 h ]

Original Secondary Outcome: Same as current

Information By: Prince of Songkla University

Dates:
Date Received: November 8, 2010
Date Started: September 2009
Date Completion:
Last Updated: October 8, 2013
Last Verified: October 2013